Free Air CO2 Enrichment of potato (Solanum tuberosum L.): development, growth and yield

Abstract A FACE (Free Air CO 2 Enrichment) experiment was carried out on Potato ( Solanum tuberosum L., cv. Primura) in 1995 in Italy. Three FACE rings were used to fumigate circular field plots of 8 m diameter while two rings were used as controls at ambient CO 2 concentrations. Four CO 2 exposure levels were used in the rings (ambient, 460, 560 and 660 μmol mol –1 ). Phenology and crop development, canopy surface temperature, above‐ and below‐ground biomass were monitored during the growing season. Crop phenology was affected by elevated CO 2 , as the date of flowering was progressively anticipated in the 660, 560, 460 μmol mol –1 treatments. Crop development was not affected significantly as plant height, leaf area and the number of leaves per plant were the same in the four treatments. Elevated atmospheric CO 2 levels had, instead, a significant effect on the accumulation of total nonstructural carbohydrates (TNC = soluble sugars + starch) in the leaves during a sunny day. Specific leaf area was decreased under elevated CO 2 with a response that paralleled that of TNC concentrations. This reflected the occurrence of a progressive increase of photosynthetic rates and carbon assimilation in plants exposed to increasingly higher levels of atmospheric CO 2 . Tuber growth and final tuber yield were also stimulated by rising CO 2 levels. When calculated by regression of tuber yield vs. the imposed levels of CO 2 concentration, yield stimulation was as large as 10% every 100 μmol mol –1 increase, which translated into over 40% enhancement in yield under 660 μmol mol –1 . This was related to a higher number of tubers rather than greater mean tuber mass or size. Leaf senescence was accelerated under elevated CO 2 and a linear relationship was found between atmospheric CO 2 levels and leaf reflectance measured at 0.55 μm wavelength. We conclude that significant CO 2 stimulation of yield has to be expected for potato under future climate scenarios, and that crop phenology will be affected as well.